Dampers have been used for many years to regulate the amount of air that flows through an air delivery or distribution system. In some applications, dampers are used to regulate or block airflows containing pollutants, chemicals, contaminants and other hazardous materials. To be effective, particularly in clean environments, dampers must block all of the hazardous airflows to ensure that workers or customers are not exposed to harmful materials, which can lead to serious health problems and possibly death.
One known damper includes an annular frame, a circular blade or a pair of semi-circular “butterfly” blades, and an annular, rigid backstop. An elastomer material is attached to an outer portion of a face of the damper blade. The annular backstop or ridge extends inwardly from the inner surface of the frame and into the aperture defined by the frame, i.e., into the path of the airflow. The backstop is provided for sealing purposes and to limit the rotation of the circular blade. When the blade is rotated to close the damper, the material attached to the face of blade hits the backstop. In other words, a seal is formed by rotating the blade, thereby pressing the elastomer material between the face of the blade and the backstop. Thus, the backstop is an integral component with certain known dampers. Without the backstop, the blade may rotate beyond the intended stopping point and a seal would not be formed.
These types of dampers have a number of shortcomings in their design and isolation capabilities, particularly when used to block airflows having pollutants, contaminants and other hazardous materials. The effectiveness of a damper that relies on forming a seal with radial pressure or rotational force to push the blade and seal material against the backstop depends on a number of factors.
For example, a damper that uses a conventional wiper-type seal configuration typically requires more complicated components and techniques to attach the wiper seal component to the damper blade. Further, a wiper configuration is typically less effective since there can be problems resulting from the seal detaching from the blade. Additionally, a circular blade having a wiper-type seal attached thereto and backstop components must be manufactured to precise tolerances so that the seal material attached to the blade and the upstanding backstop consistently sealingly mate with each other to form a seal. The backstop and the blade seal may not properly mate with each other if the outer annular sections of the blade and the sealing ridge are not properly designed within the required tolerances. These problems can result in leaks that contain harmful materials, small amounts of which can be problematic. Additionally, traditional damper designs do not optimize air flow when the damper is open. More specifically, when the damper is open, the ridge or backstop extending inwardly from the inner frame surface extends into the path of the airflow, thereby inhibiting air flow.
Other known dampers utilize an integrally formed roll formed aluminum sealing ridge. The aluminum ridge extends around the inner surface of the damper frame. A seal is formed by an outer edge of a blade contacting the aluminum roll formed ridge. These dampers, however, do not provide adequate seals, particularly when air tight seals are required. For example, the resulting seal can be improved since the outer edge of a metal blade interfaces with a ridged metal material). Minor manufacturing variations can cause leaks through these “metal on metal” seals.
Accordingly, there exists a need for an isolation damper that can reliably provide an air tight or zero-leakage seal to effectively block harmful or dangerous air flows when the damper is closed, and that improves airflow when the damper is open.